Centrifugal pump



Jan. .8, 1952 E. R. wlLFLEY ETAL. 2,581,504

CENTRIFUGAL PUMP Filed Dec. 1G, 1949 5 Sheets-Sheet 1 BY John Aldred 1r.

ATTORNEY E. R. WILFLEY ETAL Jan. 8, 1952 CENTRIFUGAL PUMP 5 Sheets-Sheet2 Filed Dec. 16, 1949 ATTORNEY Jan. 8, 1952 E. R. wlLFLEY Erm. 2,581,504

CENTRIFUGAL PUMP Filed Deo. 16, 1949 5 Sheets-Sheet ."5

Fig. 4.52

Fig. 5.

INVENTOR Elmer R. Wi|fley BY John L. Aldred jr.

mmm

ATTORNEY E. R. WILFLEY ETAL CENTRIFUGAL PUMP 5 Sheets-Sheet 4 Filed Dec.16, 1949 INVENTOR Elmer R. Wilfley BY John L. Aldr'ed jr. mmwww Jan. 8,1952 E. R. wlLFLr-:Y l-:TAL

CENTRIFUGAL PUMP 5 Sheets-Sheet 5 Filed Dec. 16, 1949 lNvENroR Elmer R.Wilfley BY John L. Aldred 1r.

ATTO R N EY Patented Jan. 1.952

UNITED sTATEs yPATENT oFFlcE z,5s1,5o4

CENTRIFUGAL PUMP Elmer R. Wilfiey and John L. Aldred, Jr., Denver,Colo., assignors to A. R. Wiliey and Sons, Inc., Denver, Colo., acorporation of Colorado Application December 16, 1949, Serial No.133,336

Claims. l

This invention relates to centrifugal pumps and in particular to thatclass thereof which avoid the use of a frictional seal or packing glandbetween the impeller shaft and the pump housing, to render such pumpsserviceable for pumping corrosive liquids or liquids carrying grit orsand. Such pumps are usually referred to as sand or slurry pumps and anexample thereof is shown in the U. S. Patent to Wilfley, No. 1,976,532.

That patent shows a sand pump in which the impeller-carrying shaft has asleeve valve surrounding it that is shiftable in an axial direction uponthe shaft to close and to open alternately an annular clearance betweenthe impeller shaft and the surrounding portion of the pump housing. Thesleeve valvel is normally held by spring pressure in sealingrelationship with the housing when the pump is not operating. As soon asthe impeller shaft starts rotating, centrifugally operated pivotedweights retract the sleeve valve from its seat against the pressure ofthe spring Where it remains while the pump is running. Leakage throughthe thus open annular clearance between the shaft and the housing issought to be discouraged by an auxiliary impeller rotating coaxiallywith the impeller shaft to create hydraulic pressure that opposes thetendency of leakage of liquid or slurry through that clearance. Becauseof that function, the auxiliary impeller is herein referred to as asealing impeller. When the pump is stopped, centrifugal force on thepivoted weights wanes with the result that the spring reasserts itspressure to shift the sleeve valve into position for closing the annularclearance between the shaft and the housing.

Such sealing impeller is shown generally in U. S. Patent No. 1,346,926to Wilfley, with that impeller rotatable in a surrounding chamber.

This invention, while availing itself of teachings contained in thesepatents, embodies them in a sand pump of novel characteristics offeringimportant functional and structural improvements.

An important object of this invention is to produce a sand pump ofgreater efiiciency than any of the aforementioned patented pumps per se.Without sacrificing the lbest features in them. The term efficiency isherein used in a somewhat specific sense denoting the ability of andpurpose of the sealing impeller of discouraging or preventing entranceand entrainment of air into the pump during operation, inasmuch as suchair entrainment adversely affects the capacity of 2 the pump efficiencyespecially when operating on a suction lift.

Therefore, this invention relates more particualrly to improvements inleak-sealing impeller devices as well as in improvements of the sealingeffectiveness of such a pump.

Another object is to embody a sealing impeller in the sand pump in sucha manner as to improve and facilitate the assembly of the pump.

In the pump disclosed in the Patent No. 1,346,926, the sealing impellerrotates in and is surrounded by an auxiliary chamber herein termedsealing chamber which at one side communicates with the interior of thepump housing and at the other side with the atmosphere. That is to say,that side of the chamber which faces the interior of the pump forms anannular clearance or passage around the impeller shaft and so does thatside of the chamber which faces in the opposite direction, namelyoutwardly. These annular clearances then constitute respectively aninner passage and an outer passage, the inner passage communicating withthe interior of the pump, and the outerpassage communicating with theouter atmosphere although automatically closed by a leakage-preventingsleeve valve whenever the impeller shaft stops rotating. The sealingimpeller itself comprises a disc having blades or vanes extendingradially upon each face of the disc. The vanes facing the interior ofthe pump housing have a shorter effective length than the vanes facingoutwardly, and the set of shorter vanes will herein also be termed theinner vanes while the set of longer vanes will be termed the outervanes. Both sets of vanes exert centrifugal forces upon a body of liquidin the chamber although in directions opposed to each other, in that theforce exerted -by the inner blades opposes that exerted by the outerblades, the force from the outer blades however being in excess of theforce from the inner blades because of the differential in electivelength between the two sets of blades, the concept being that the forcefrom the inner vanes would tend to push liquid outwardly from the pumphousing, while a somewhat greater force from the outer vanes would tendto push the liquid inwardly into the pump housing.

According to the concept of operation of the patented sealing impelleratmospheric air seeks to enter the interior of the pump housing by wayof passing from the side of outer vanes around the peripheral edge ofthe disc to the side of inner vanes, but this is to be counteracted,prevented or discouraged by the centrifugal force size-screening zone.

imparted to liquid or pulp in the chamber by the inner vanes. However,this condition is maintainable in a balanced manner only if, accordingto the concept of the patent, the outward force from the inner vanes iscounteracted by the inward force from the outer vanes so that theresultant equilibrium of forces might maintain the desired annular bodyof sealing liquid or pulp around the marginal portion of the disc. Theconcept according to the patent is that with the centrifugal forceimparted to the sealing liquid by the outer (longer) vanes beingsomewhat greater than that imparted by the inner v(shorter) vanes,atmospheric air enters the chamber only on the side of the outer vanesby interfacial contact with the liquid or pulp which on that siderecedes towards the periphery of the disc although not exposing it.Indeed, if the pump and the sealing impeller were to function asproposed by the patent, the sealing liquid on the side of the outervanes should recede to a point where a balance is reached between thepressure of the liquid and air on the side of the inner vanes.

It was expected that this patented bladed sealing impeller would stirliquid, suspended solids. and air in the chamber into such a churnedmixture that the churned mass or pulp would act as a seal againstair-leakage into the pump. But such was not the case to an extent togive assurance against such leaks, nor did the phenomenon of equilibriumdevelop to the extent expected. Therefore, it is an important object ofthis invention to improve upon that air-seal to make it more effectiveand dependable while combining it with the shiftable sleeve valvemechanism of the Patent No. 1,976,532.

This object is realizable by providing the sealing chamber withsolids-screening means or passages for controlling the particle size ordimension of solids allowed to enter the chamber from the pump, as wellas with relief duct means leading from the periphery of the sealingchamber into the inlet portion of the pump housing, and so proportionedrelative to the screening passages that a suspension of substantiallyuniform density is maintained in the chamber for sealing purposes. Thefunction of the screening means is to arrest and reject oversize solidsto prevent them from reaching the blades of the sealing impeller disc.Such means may include satisfactorily successive and progressivescreening zones including a primary size-selecting zone characterized byan annular ingress opening of predetermined size followed by a secondarysizescreening zone characterized by an annular throat. These means areexemplified by a chamber that is defined on its pump-end by a platehaving an unular rib or ridge laterally extending toward the disc toform therewith thethroat of the secondary zone, that is a throat ofliquid connecting an inner smaller annular pool of primary sizedsuspended solids entering it from the pump (through the ingress openingof the primary size-selecting zone) and an outer larger annular pool ofsuch solids small enough to have passed through the primarysize-selecting zone and then through the throat of the secondary This isaccomplished by having the width of the ingress opening to the chamber apredetermined size and the width of the throat less than that of theingress opening.

If suspended solids 'are continually supplied to the chamber, they willaccumulatetherein and intimately displace the liquid until they ,dil thedilution of the suspended solids within the chaml ber. Such means areexemplified by an egress duct or relief duct leading from the chamberback to the inlet side of the pump with that duct carefully dimensionedso as to allow suspended solids from the chamber to pass therethrough atsuch a rate that the chamber is neither evacuated of its liquid nor hasthe concentration of its solids unduly increased. To that end, theegress duct must have its width or cross-sectional dimension greaterthan that of the throat and of the ingress opening but not large enoughfor the blades to pump liquid from the chamber at a rate faster than itflows into the chamber through the ingress opening and thesize-screening throat. Again, the inlet end of the egress duct is placedadjacent the periphery of the sealing chamber and the duct extendsgenerally radially of the chamber to insure bleeding off of suspendedsolids from the chamber back to the pump with sufficient centrifugalforce to prevent plugging of the duct.

Thus, by the use and in the practice of this invention there is providedan annular turbulent pool of suspended solids in which the periphery ofthe bladed disc of the sealing impeller is submerged at all times duringits rotation, with those solids controlled as to maximum size and withthe density of the suspension maintained substantially constant withthat of the suspension being pumped by the pump. The density of thesuspended solids is also maintained on the suspension-receiving face ofthe disc while on the opposite face of the disc air is received which isalso rendered highly turbulent by the longer blades on that face. Themass of turbulent air engages against the denser pool of suspendedsolids in which the periphery of the disc is submerged and issubstantially repelled thereby. n other words, the air that is carriedby the outer vanes is being separated centrifugally from the solids andliquid mixture. If the pump is operated with negative pressure at theinlet end, the air mass between the air-contacting face of the disc andthe chamber will be greater in extent or in diameter than the extent ofsubmergence of K the periphery of the disc. Reversely, if the pump isoperated with positive pressure, the extent of the air mass Will be lessthan that of the extent of submergence of the disc. That is to say, forthe seal to operate properly the diameter of the cylindrical air-liquidinterface must be smaller than the diameter of a circle defining theouter ends or tips of the long vanes on the outer side of the disc,since these tips must be surrounded by liquid in order to enable them tomaintain centrifugal action upon the liquid. However, the diameter ofthis interface will be greater when the liquid is supplied to the pumpunder a negative head than when it is supplied under a positive head.

While some of the features of this invention render it particularlyuseful in the handling of solids-liquid suspension by the pump, thisdoes not exclude the successful handlingof liquids which are free ofsolids in a pump embodying the essence of this invention. i

In the Wilfley Patent No. 1,976,532, the pump housing comprises a mainbody portion through which .extends the free end of the impeller shaft,and e 4envier portion removable from the body portion for outwardlyremoving the pumping impeller from the free end of the shaft. Thesealing impeller is formed by an inward hollow extension of the hubportion of the pumping impeller and has blades that extend from theinner face of the hollow of that extension. The outer face of thisextension presents a complementary portion of the inner contour of theinlet end of the pump housing so these two impellers comprise a fairlycomplex assembly. When dismantling the pump, the pumping impeller andits unitary sealing impeller must be removed from y the free outer endof the impeller shaft and from `the pump housing in an outward axialdirection, while the impeller shaft itself together with its sleevevalve mechanism must be removed axially in the opposite direction.

Furthermore, that pump includes a removable shaft-carrying componentwhose inner end lodges in and is carried by the pump housing through asealing gland, while the outer end of that component is supported by thepump base. This shaft-carrying component comprises as one assembly ailxed tubular shell in which the impeller shaft is journalled and a cageextendingfrom the pump-end of this shell into the intake portion of thepump housing so as to surround the sleeve valve mechanism. The cage ineffect constitutes an inward extension of the shell and its free endrepresents that end of the shaft-carrying assembly that lodges in thepump housing. The free end of the cage is closed by an annular end platesurrounding the impeller shaft and presenting inwardly within the cagean annular seat for the sleeve valve while its outer face is formed withan annular recess into which extends the sealing impeller.

Therefore, in such a pump, only after the pumping impeller with itssealing impeller has been disconnected and removed from the free end ofthe shaft. can the shaft-carrying assembly be removed with its shell inthe opposite direction from the pump housing. In other words, such apump comprises as main assembly components: (a) the pump housing andbase; (h) the unitary pumping and sealing impellers; and (c) theshaft-carrying assembly with its valve mechanism.

It is among the objects of this invention while improving the sealingeffectiveness of such a pump, to also improve it structurally in such amanner as to facilitate its assembly and to render it more readilyaccessible; in short to provide an improved sealing impeller arrangementyet without requiring any substantial changes in the basic dispositionwith respect to one another of the main assembly components (a), (b),and (c), of the pump.

These objects are attainable by adding to the closure plate of the cagea contour-shaped plate such that between it and the closure plate thereis formed an auxiliary annular chamber to surround a separate sealingimpeller carried by the impeller shaft alongwith the pumping impeller.That side of the contour plate that faces the interior of the pumppresents a fixed streamlined portion of the inner contour of the inletportion of the pump, even though constituting a part of theshaft-carrying assembly l c) Thus the sealing impeller is held in placewithin its chamber and is made to rotate with the pumping impeller shaftby a coupling connection between it and the pumping impeller whichlatter is removably ilxed to the free end of the shaft. This wnnelwibetween the pumping impeller and the sealing impeller establishes itselfin the course of assembling the pump. That is, when the pumping impelleris disconnected and removed from the shaft, such removal will disconnectit from its driving engagement with the sealingimpeller. The sealingimpeller in turn is then removable from the pump housing as part of theremovable shaft-carrying assembly. In other words, the pumping impellerand. the sealing impeller interengage at their hubs which haveinterengaging complementary scalloped faces, that is one hub has ascalloped end which engages with an abutting complementary scalloped endof the other hub. And further, a cushioning annulus is interposed andcompressed between these hubs.

The best embodiment of the invention now known to us has been chosen asan example to describe herein for illustrative, but not limiting.purposes, since modifications obviously can be made therein so long asthey do not depart from the scope of the appended claims and theirequivalents. That embodiment is illustrated in the accompanying drawingsin which:

Fig. 1 is a part-sectional longitudinal side view of the pump unitshowing the improvements in the sealing means within an improvedstructural environment.

Fig. 2 is a part-sectional view of the pump shown in Fig. 1, althoughexploded. Fig. 3 is an enlarged detail view of that portion of the pumpunit which comprises the improved sealing means.

Fig. 4 is a view similar to Fig. 3, with pressure conditions indicatedin the sealing chamber corresponding to a. highly negative pump inletpressure.

Fig. 5 is a view similar to Fig. 3, with pressure conditions indicatedin the sealing chamber corresponding to a less negative pump inletpressure.

Fig. 6 is a view similar to Figs. 3, 4, 5, although further enlarged toillustrate more clearly the operating conditions, especially thescreening conditions, in the chamber.

Fig. 7 is a sectional detail view of the sealing impeller.

Fig. 8 is a View of the sealing impeller taken on line 8--8 of Fig. 7.

Fig. 9 is a view of the sealing impeller on linel 9-9 of Fig. 7.

Fig. 10 is a view of the sealing impeller taken on line Ill-I 0 of Fig.9.

Referring to Fig. 1 the invention is embodied' in a pump unit in whichan impeller shaft I0 is rotatable in a stationary and generally tubularstructure II which has its front end extending into and is supported bya pump housing I2 while its rear end is supported by a bearing lug I3'constituting an integral part of the rear end portion of a base I 4 ofthe pump unit. yIn fact this base Il is also integral with whatconstitutes the in take housing portion I 2a of the pump housing. Abearing cover I3a holds the tubular structure in place upon the bearinglug I3. A discharge housing portion I5 it attached to the intake housingportion I ia and surrounds an impeller I6 fastened to the front end ofshaft I0. An intermediate annular housing portion I1 is interposedbetween the housing portions-I2l and I5 and is sealed against them as byrubber ringsr I8 and I9. The

20 while the intake neck for the intake housing .portion is not shown inthe drawing. l The 'tubular structure II is sealed against thev 2| heldby a gland 22 secured as by lugs 23 fastened by bolts 24 to the intakeportion. The tubular structure is held against longitudinal displacementalthough longitudinally adjusted by a' stud 25 screwed into the bearinglug I3 and secured to the tubular structure by means of a bifurcated lug26 extending integrally from the tubular structure as well as by meansof a pair of lock nuts 21 and 28 tightened from opposite directionsagainst the bifurcated lug. The tubular structure I I comprises what mavbe termed a shaft-bearing section 29, a valve control section 30, and asealing impeller section 9|. The shaft bearing section 29 is so termedbecause it comprises a tubular member 32 having a front roller bearing33 and a rear roller bearing 34 in which bearings rotates the impellershaft although secured against axial displacement. The valve controlsection 30 comprises a cage 35 fastened by flange and bolt connection35=L to the front end of the tubular member 32, and has a bottom opening36. This cage houses a centrifugally controlled automatic valveactuating mechanism collectively designated as M and which is known perse as in the pump unit of the aforementioned Wilfiey Patent No.1,976,532. Such i mechanism comprises an annular sleeve valve 31`yvhichis slidable in axial direction upon the impeller shaft I so as to openor close an annular gap or clearance 38 (more clearly shown in Fig. 6)and defined by an annular closure plate P which surrounds the impellershaft and is unitary with and fastened to the cage l35.

The sleeve valve member 31 is unitary With a bell-shaped member orshield 39 which in turn surrounds the valve-actuating centrifugalmechanism proper. The shield 39 is movably connected to the axiallynon-shiftable shaft ||l by means of annular diaphragm 49. That is tosay, the outer edge of this diaphragm is connected internally to shield39 as at 4|, while the inner edge of the diaphragm is connected as at 42to a sleeve member 43 which in turn is xed to the shaft. This diaphragm40 by reason of its deformability allows for axial movement of the valvemember and shield as a unit relative to the shaft by action of pivotallymovable centrifugal weight members 44. Each of these weight members(only one of which is visible in Fig. l) is movable about a pivot 45mounted upon and unitary with the sleeve member 43 and thus with theshaft lll.

vHence when the shaft rotates the outer or weighted ends 44 of theweight members move outwardly away from the shaft while their inner ends44b engaging the interior of shield 39 move the valve member 31 axiallyto open position against the pressure of a coil spring 46 whichsurrounds the shaft and which returns the valve member to closedposition when the rotation of the shaft stops and the centrifugal effectof the weight members ceases.

The sealing impeller section 3| constitutes an annular chamber` 41formed by the closure plate P and by what is herein termed a contourplate 48. Within this chamber rotates a sealing impeller 49 fixed to theshaft in a manner more clearly shown in detail Figs. 3 to 6. That is thehub 4i!a of this sealing impeller is connected to the shaft by beingconfined 4between the inner end of sleeve member 43 and the adjacent endportion llia of the hub of impeller i6. Both the hub of the sealingimpeller and of the pump impeller have at their mutually adjoining endsa wave-like formeticn presenting scallops Si and Sz respectively whichare complementary to each other in such a manner that scallops Si extendinto the recesses between scallops Sz and vice versa so that therotation or torque of the shaft I0 is transmitted through the impellerI6 to the sealing impeller 49 so that both impellers will rotate as aunit with the shaft. Between the two complementary scalloped faces asindicated by scallops S1 and S2 there is interposed an annulartorque-transmitting filler member 5|! of rubber or similarly resilientlydeformable cushioning material which renders unnecessary any accuratemachining or interfitting between the interengaging hub portions ofimpellers and 49.

The sealing impeller section 3| with its sealing impeller 49 and itschamber 41 embodies certain features which more clearly presentthemselves in detail Figs. 3 to l0. Mainly these features involve theprovision of an ingress duct 5| leading from the inlet side of the pumpinterior centrally into the chamber 41, and an egress duct 52 hereinalso termed a relief duct leading from the margin of chamber 41 back tothe inlet side of the pump interior.

The sealing impeller 49 comprises a disc p0rtion 53 integral with thehub 49". At its outer face and facing away from the interior of the pumpthe disc portionhas integral therewith radial extending long ribs hereinalso called the long vanes 54 designated by their length L1. The vanes54 alternated with wedge-shaped lugs 55 interposed between respectiveouter end portions of the vanes 54 and are `also integral with the discportion 53. At its inner face, that is facing the interior of the pump,the disc portion has integral therewith radially extending short ribsherein also called the short vanes 56 designated by their length L2. Theposition of the long vanes relative to the short vanes radially is suchthat the short vanes start a distance di from the inner end andterminating a distance da from the outer end of the long vanes. Thus thelength L1 of the long vanes represents the4 sum total of the lengthdi-i-La-l-dz.

The contour plate 48 surrounds the impeller hub portion constitutingtherewith the annular ingress opening 5I which is characterized by awidth w1. Facing the interior of chamber 41 the contour plate is formedwith an annular rib 51 extending towards the disc portion 53 of thesealing impeller and terminating a distance wa therefrom which ischaracteristic of an intermediate passage 58 between the ingress andegress ducts of the chamber. The egress ducts 52 are formed in themarginal portion of the contour plate 48 and comprises a radiallyextending portion 52a and a horizontally extending portion 52". Theegress ducts are also characterized by a-width w3. The width wi ofingress duct 5| is smaller than the width wz of the intermediate passage58, and width w3 in turn is smaller than wz. In this Way if the pumphandles a pulp or liquid-solids mixture containing coarse and finesolids, the ingress opening will permit the passage therethrough only ofa fine fraction into the sealing chamber 41. In the course of operationthis ne fraction will pass from the central part to the outer parts ofchamber 41 by way of the second or intermediate passage 58, and finallyleave the marginal portion of the chamber 41 by way of the egress ducts52. In this way a certain portion of solids-carrying liquid of suitablecharacteristics is allowed to circulate within the pump with respect tokeeping the coarse particles ofthe pulp out of the sealing chamber 41has been illustrated by indicating the mixture of solids entering, thepump as being characterized by coarse particles 50 and ne particles 5l,the fine particles only being allowed by reason of the width w1 to enterinto and pass through the sealing chamber 41.l

Operation of the sealing impeller section As the pump starts running thevalve controlled mechanism M acts to shift the valve member 31 outwardlyand away from its seat on plate P, thus shifting it from its Fig. 3(closed) position to its Fig. 6 (open) position. At the same time thesealing impeller 49 makes its action felt upon the liquiderliquid-solids mixture that iills the sealing chamber 41 by impartingthereto centrifugal effects which cause an annular body of sealingliquid to form and to be maintained in the sealing chamber substantiallyas represented in Fig. 6 which body of liquid surrounds and immerges themarginal portion of the disc 53 of the sealing impeller. As a result ofthe interaction of hydrostatic pressures and centrifugal forces upon theliquid in chamber 41 there establishes itself an equilibrium manifestingitself in the fact that a portion of the outer face F1 of the sealingimpeller is exposed to the atmosphere through the valve gap 38, whilethe peripheral portion and the opposite or inner face Fa are surroundedand contacted -by the liquid. Under operating conditions assumed toexist according to Fig. 6 the extent of exposure to air of face F1 isindicated by an area of the diameter D1 Which is smaller by thedifferential 2A than the diameter D: of the disc 53. Thus at its outerface the 'disc is immersed to a depth A representing the seal properwhereby entry of atmospheric air into the pump is. prevented. While theextent of disc immersion A shown in Fig. 6 corresponds to or representsa given set bif operating conditions, these conditions may allowed tovary within certain safe limits in accordance with a variation of thediameter D1.- Thus for a given pump there exists a latitudeconcerningvariations of its operating conditions within which the liquid seal willfunction properly, such variations being mainly due to differences inthe pressure under which the liquid is being supplied to the pump andwhich is herein briefly termed the supply pressure. 'That is to say, thesupply pressure and therefore the extent of immersion A of the disc 53may be allowed to vary provided that the marginal portion of the discdoes not become denuded of sealing liquid and. on the other hand,provided that the sealing liquid is not allowed to cover so much of theouter face F1 of the disc as to risk its escape through the valve gap38. Such safe limits in terms of diameter of the exposed portion of theface F1 of the disc are indicated in Figs. 4 and 5. Fig. 4 indicates amaximum safe diameter D3 corresponding to a relatively lower supplypressure while Fig 5 indicates a minimum safe diameter D1 correspondingto a relatively higher supply pressure. Again, the range of these limitscan be altered by a change in the relative lengths L1 and L2 andrelative positions of the impeller vanes 54 and 55.

The function of the sealing impeller is of especial significance asinitially pointed out when the supply pressure is negative, that is whenthe pump operates under a suction lift. Let it be assumed then that theFig. 6 condition representssuch a case. Withfhydraulic operatingequilibrium set up in the sealing chamber 41 thereis established an airspace A atthe outer face of the sealing impeller which air space isi'`definable by the circular area corresponding to diameter D1 and by acylindrical area C representing the air liquid interface. Indeed, thecentrifugal force which tends to compress the annular liquid sealingbody in chamber 41, by its very compression also rejects air that mighthave gotten entrapped in the liquid, this diametrically maintaining theinterface C substantially sharply as such. Y

The equilibrium conditionswhich maintain the annular body of sealingliquid around the margin of the disc 53 are due to the effect of thevanes 56 at one side of disc 53 being shorter than the vanes 54 at theother side of the `disc-- in other words, due to the chosen ratio oflengths Li/Ln of the vanes as well as. due to the disposition radiallyof the two sets of vanes relative to each other. Consequently, thecentrifugal force imparted to the water by the shorter vanes is lessthan although counteracting that imparted by the longer vanes, therespective ducts of the centrifugal forces exerted by the two sets ofvanes being indicated as by the arrows R1 and Rz in Fig. 6. Atmosphericair communicating with the air space A through the valve gap 38 has thetendency to enter the inlet side of the pump housing in response to thenegative supply pressure or suction. therein, .but is prevented fromdoing so by the counteracting centrifugal force imparted to the sealingliquid by the shorter vanes. In other words, since the centrifugal forceRz is greater than the opposed centrifugal force R1 air enters the spaceA following the centrifugally receding liquid at the outer face of disc53 until a balance is reached between the combined pressures of waterand of air at the outer face F1 of disc 53 and the water pressure at theopposite or inner face F: of the disc. In this way atmospheric air isprevented from passing from the outer face F1 past the periphery of disc53 to the inner face F2 thereof due to the annular body of sealingliquid surrounding the periphery of the disc. Hence, the very rotationof the impeller shaft while holding the valve member 31 in its openposition, also hydraulically seals the inlet side of the pump housingagainst entrance of air even though the pump may have to rely upon thesuction tto drawthe water or liquid-solids mixture into the pump.

It should be understood that entrained air is centrifugally separatedfrom the liquid or pulp by the action of the long vanes of the sealingimpeller so that no air by way of entrainment in thef liquid will reachthe intake side of the pump and impair the suction lift thereof.Furthermore, the diameter D1 of the air-liquid interface C must be nogreater than the diameter D2 which denes outer tips of the long vanes54, since at least these tips must be immersed in or be surrounded byliquid in Yorder that centrifugal action upon the liquid and theformation of the annular body of sealing liquid may be sustained in thesealing chamber. However, the air space diameter D1 will be greater whenthe pump operates under a suction lift, that is negative supply head,than it will be with a positive supply head.

The ability of the short and the long vanes of the sealing impeller tomaintain a liquid seal against a negative or a positive supply headdepends upon their respective tip radii represented by diameters Dz andD respectively as well as.

upon their respective lengths L1 and Lz. By varying these structuralfactors for a given R. P. M. of the pump a seal to suit various supplypressure conditions results. For instance, ii a liquid seal wererequired against a highly negative supply head for a given R. P. M., thediameter D5 of the short vanes would be increased to a maximum as wellas its length Lz thus increasing their pumping effect, while thedimension of the long vanes remain as is. If the seal were to be for ahighly positive supply head, the pumping effect of the short vanes wouldbe minimized to the point that only the surface roughness of the face Fzof the disc remained to produce a slight pumping effect, so thatsubstantially theI full length of the long vanes Would remain effectivein producinga pressure to balance the intake pressure of the pump.

For practical purposes. for example, three different combinations oflengths of the vanes may be provided, namely one for a high positiveintake head, one for a negative intake head, and an intermediate one fora normal or average intake head. The variations in proportioning willlie in the dimensionng of the short vanes for given dimensions of thelong vanes.

Fig. 6 represents the pump as handling a liquidsolids mixture or pulpcontaining relatively coarse solid particles designated as a group bythe letter E, along with relatively finer particles designated as agroup by the letter Ez. The action of the sealing impeller causes aquantity of pulp from the intake side of the pump to be recirculatedthrough the sealing chamber, the pulp entering through the ingress duct5| and returning to the intake side through the egress openings.

In considering the functioning of this recirculation of pulp through thesealing chamber, a distinction is to be drawn as between the respectivewidths and the through-flow areas of the ingressand egress-ducts. Theegress area should not be so large that the vanes 54 and 56 will pumpliquid through that area faster than it enters through the ingress area.Indeed, the proportioning oi these areas should be such that the sealingchamber and sealing vanes have a continual supply of pulp substantiallyfree of entrained air to work on. `Yet, the width w3 of the egress ductshould be greater than the width wz of the intermediate passage 58 aswell as greater than the width w1 of the ingress duct. The width wz inturn should be greater than width w1. Width w1 again is such that itWill selectively admit into the sealing chamber only smaller size solidsEz, the ingress duct thus in eifect constituting a primary sizingscreen, While the width wz constitutes a secondary screen for sizing ofparticles after they have passed through the ingress duct. The widths wzand w1 represent the clearance between stationary and rotary parts, sothat particles entering these clearances encounter considerable relativevelocity as between the side walls of these clearances. If particlesshould find their way into these clearances of such size that would tendto stick or clog therein, the relative motion between the side wallswould abrade the particles to such size that they would pass through.Therefore, as the clearances wz and wi are less than the clearance wa,the particles will pass through the egress ducts, being carried byliquid passing through the sealing chamber. Admittingto andrecirculating through the sealing chamber a thus sized pulp fractioncontaining finer particles to the exclusion of the coarser ones insuressmooth and uncongested operation of and less wear and tear upon thesealing chamber and the sealing impeller.

We claim:

1. A centrifugal pump having a pump housing and a pumping impellercarried by a rotatable shaft extending at one end into the pump housing,an auxiliary impeller disc on the shaft with blades laterally extendingfrom each face of the disc, an annular chamber surrounding the auxiliaryimpeller having restricted ingress opening thereinto around the shaftfrom one direction for suspended solids from the pump and from anotherdirection for air from outside the pump housing together with an egressduct leading back to the pump housing from a point farther away from theshaft than the ingress opening.

2. Apparatus according to claim 1, wherein the blades on the face of thedisc nearest the pumping impeller are shorter than the blades on theother face and between the shaft and the inner ends of the shorterblades the chamber narrows toward the disc to provide a solids-screeningpassage for rejecting oversize suspended solids from reaching theshorter blades.

3. Apparatus according to claim 1, wherein the blades on the face of thedisc nearest the pumping impeller are shorter than the blades on theother face and between the shaft and the inner ends of the shorterblades the chamber narrows toward the disc to provide a solids-screeningpassage for rejecting oversize suspended solids from reaching theshorter blades with the width of that passage being less than that ofthe ingress opening for suspended solids.

4. Apparatus according to claim 1, wherein the blades on the face of thedisc nearest the pumping impeller are shorter than the blades on theother face and between the shaft and the inner ends of the 'shorterblades the chamber narrows toward the disc to provide a solids-screeningpassage for rejecting oversize suspended solids from reaching theshorter blades with the width of that passage being less than that ofthe ingress opening for suspended solids while the width of the egressduct is greater than that of the ingress opening.

5. Apparatus according to claim l, wherein the blades on the face of thedisc nearest the pumping impeller are shorter than the blades on theother face with suspended solids being supplied to the shorter bladesfrom the suspended-solids ingress opening while air is supplied to thelonger blades from the air ingress opening whereby the chamber is lledwith an agitated pool of suspended solids from which a quantity of suchmixother face and between the shaft and theinner ends of the shorterbladesthe chamber narrows passage with a. largerpool of screenedsuspendedv solids enclosing the periphery of the disc -to which air issupplied past the longer blades on the disc.

7. A centrifugal pump having a pump housing supported from a base and apumping impeller carried by a rotatable shaft extending at one end intothe pump housing and at its other end supported in a tubular shellmounted from the base, automatically shiftable valve means between -theshaft and the pump housing for sealing space therebetween when the pumpstops and opening it when the pump starts, an auxiliary impeller disc onthe shaft between the valve means and the pump housing\with bladeslaterally extending from each face ofthe disc, and an annular chambersurrounding the auxiliary impeller having restricted ingress openingthereinto around the shaft from one direction for suspended solids fromthe pump and from another direction for air from the valve meanstogether with an egress duct leading back to the pump housing from apoint farther away from the shaft than the ingress opening.

8.Apparatus according to claim 7, in which the pump impeller and theauxiliary impeller have inter-engaging hub portions for jointly rotatingwith the shaft.

9. A centrifugal pump according to claim 7. in

shiftable in the tubular structure with a pump impeller carried by andfastened to the outer free end of the shaft surrounded by the housing,and further having automatically actuated sealing valve means forautomatically opening and closlng an annular gap between the shaft andthe I housing which comprise an annular valve member axially shiftableupon "the shaft forV opening and closing the gap and oentrifugallyactuated mechanism surrounding the shaft and disposed within the innerend portion of the tubular structure 'c for shifting the valve member toautomatically open and close the gap when the pump starts and stopsrespectively, said pump further having auxiliary impeller means rotatingwith the impeller shaft to counteract leakage through the gap;characterized by the fact that the tubular shaft-carrying structure hasat its extreme inner end an annular chamber having a main annular whichthe pump impeller and the auxiliary im-V peller have inter-engaging hubportions for jointly rotating both impellers, with the addition of anannular member of resiliently deformable rubber-like material interposedand compressed between the interengaging hub portions.

10. A centrifugal pump having a base member, a pumphousing mounted uponthe cuter end of the base member, a substantially tubular shaftcarryingstructure having its outer end supported upon the outer end ofthe basemember and its inner end supported in and by the inlet portion of thehousing and in sealing relationship therewith. an impeller shaftrotatable and axially nonwall'portion providing a seat for the valveImember, and a complementary annular wall portion constituting a part ofthe inlet portion of the housing and presenting a concave contourmerging with the inner contour of said inlet portion; and that theauxiliary impeller means comprise an impeller member rotating in theannular chamber and constituting with the shaft and with the tubularstructure an assembly unit removable as such from the inlet portion ofthe pump housing.

y ELMER a. WniFLnY.

JOHN L. Amann, JR. REFERENCES CITED The 'following references are ofrecord in the ille of this patent:

UNITED STATES PATENTS

